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98 Cards in this Set

  • Front
  • Back
Fission products that have large microscopic cross sections for capture of thermal neutrons are called... A. breeder fuels. B. burnable poisons. C. fissionable fuels. D. reactor poisons.
D
Fission product poisons can be differentiated from other fission products in that fission product poisons... A. have a longer half-life. B. are stronger absorbers of thermal neutrons. C. are produced in a larger percentage of fissions. D. have a higher fission cross section for thermal neutrons.
B.
A fission product poison can be differentiated from all other fission products in that a fission product poison... A. will be produced in direct proportion to the fission rate in the core. B. will remain radioactive for thousands of years after the final reactor criticality. C. will depress the power production in some core locations and cause peaking in others. D. will migrate out of the fuel pellets and into the reactor coolant via pinhole defects in the clad.
C.
A fission product poison can be differentiated from all other fission products in that a fission product poison... A. will be radioactive for thousands of years. B. is produced in a relatively large percentage of thermal fissions. C. has a relatively high probability of absorbing a fission neutron. D. is formed as a gas and is contained within the fuel pellets and fuel rods.
C.
A fission product poison can be differentiated from all other fission products because a fission product poison... A. has a higher microscopic cross section for thermal neutron capture. B. has a longer half-life. C. is produced in a greater percentage of thermal fissions. D. is formed as a gas and is contained in the fuel pellets.
A.
Xenon-135 is considered a major fission product poison because it has a large... A. fission cross section. B. absorption cross section. C. elastic scatter cross section. D. inelastic scatter cross section.
B.
Which one of the following is a characteristic of xenon-135 in a nuclear reactor core? A. Xenon-135 is produced from the radioactive decay of barium-135. B. Xenon-135 is primarily a resonance absorber of epithermal neutrons. C. Thermal neutron flux level affects both the production and removal of xenon-135. D. Thermal neutrons interact with xenon-135 primarily through scattering reactions.
C.
Which one of the following exhibits the greatest microscopic cross section for absorption of a thermal neutron in an operating nuclear reactor core? A. Uranium-235 B. Boron-10 C. Samarium-149 D. Xenon-135
D.
Compared to other poisons in the core, the two characteristics that cause Xe-135 to be a major reactor poison are its relatively _________ absorption cross section and its relatively _________ variation in concentration for large reactor power changes. A. small; large B. small; small C. large; small D. large; large
D.
Immediately after a reactor trip from sustained high power operation, xenon-135 concentration in the nuclear reactor will... A. increase due to the decay of iodine already in the core. B. decrease because xenon is produced directly from fission. C. remain the same because the decay of iodine and xenon balance each other out. D. decrease initially, then slowly increase due to the differences in the half-lives of iodine and xenon.
A.
Xenon-135 is produced in a nuclear reactor by two primary methods. One is directly from fission, the other is from the decay of... A. cesium-135. B. iodine-135. C. xenon-136. D. iodine-136.
B.
A nuclear reactor has been operating at full power for several weeks. Xenon-135 is being directly produced as a fission product in approximately _________ percent of all fissions. A. 0.3 B. 3.0 C. 30 D. 100
A.
Which one of the following lists the production mechanisms of Xe-135 in an operating power reactor? A. Primarily from fission, secondarily from iodine decay B. Primarily from fission, secondarily from promethium decay C. Primarily from iodine decay, secondarily from fission D. Primarily from promethium decay, secondarily from fission
C.
The major contributor to the production of Xe-135 in a nuclear reactor that has been operating at full power for two weeks is... A. the radioactive decay of I-135. B. the radioactive decay of Cs-135. C. direct production from fission of U-235. D. direct production from fission of U-238.
A.
Following a reactor trip from sustained power operation, the xenon-135 removal process consists primarily of... A. beta decay. B. gamma decay. C. electron capture. D. gamma capture.
A.
Reactor power is increased from 50 to 60 percent in 1 hour. The most significant contributor to the initial change in core xenon-135 reactivity is the increase in xenon-135... A. production from iodine decay. B. production from fission. C. absorption of neutrons. D. decay to cesium.
C.
In a shut down nuclear reactor, which decay chain describes the primary means of removing xenon135? ¥ A. 135Xe 6 135Cs n 134Xe B. 135Xe 6 ¥ 131Te C. 135Xe 6 ¥+ D. 135Xe 6 135I
A.
Xenon-135 undergoes radioactive decay to... A. iodine-135. B. cesium-135. C. tellurium-135. D. lanthanum-135.
B.
Nuclear reactors A and B are operating at steady-state 100 percent power with equilibrium core Xe 135. The reactors are identical except that reactor A is operating at the end of core life (EOL) and reactor B is operating at the beginning of core life (BOL). Which reactor core has the greater concentration of Xe-135? A. Reactor A (EOL) due to the smaller 100 percent power thermal neutron flux. B. Reactor A (EOL) due to the larger 100 percent power thermal neutron flux. C. Reactor B (BOL) due to the smaller 100 percent power thermal neutron flux. D. Reactor B (BOL) due to the larger 100 percent power thermal neutron flux.
C.
A nuclear power plant has been operating at 100 percent power for several months. Which one of the following describes the relative contributions of beta decay and neutron capture to Xe-135 removal from the reactor core? A. Primary - neutron capture; secondary - beta decay. B. Primary - beta decay; secondary - neutron capture. C. Beta decay and neutron capture contribute equally. D. Not enough information is given to make a comparison.
A.
A nuclear reactor has been operating at 50 percent power for one week when power is ramped in 4 hours to 100 percent. Which one of the following describes the new equilibrium core xenon-135 concentration? A. Twice the 50 percent power concentration. B. Less than twice the 50 percent power concentration. C. More than twice the 50 percent power concentration. D. Remains the same because it is independent of power.
B.
A nuclear reactor was operating at 100 percent power for one week when power was decreased to 50 percent. Which one of the following describes the equilibrium core xenon-135 concentration at 50 percent power? A. The same as the100 percent value. B. More than one-half the 100 percent value. C. Less than one-half the 100 percent value. D. One-half the 100 percent value.
B.
A nuclear reactor has been operating at 25 percent power for 24 hours following a 2-hour power reduction from steady-state full power. Which one of the following describes the current status of core xenon-135 concentration? A. At equilibrium B. Decreasing toward an upturn C. Decreasing toward an equilibrium value D. Increasing toward a peak value
C.
Following a two-week shutdown, a nuclear reactor is taken critical and ramped to full power in 6 hours. How long will it take to achieve an equilibrium xenon condition after the reactor reaches full power? A. 70 to 80 hours B. 40 to 50 hours C. 8 to 10 hours D. 1 to 2 hours
B.
Which one of the following indicates that core Xe-135 is in equilibrium? A. Xe-135 production and removal rates are momentarily equal five hours after a power increase. B. A reactor has been operated at 80 percent power for five days. C. Xe-135 is being produced equally by fission and I-135 decay. D. A reactor is currently operating at 100 percent power.
B.
Nuclear reactors A and B are operating at steady-state 100 percent power with equilibrium core Xe 135. The reactors are identical except that reactor A is operating near the end of core life and reactor B is operating near the beginning of core life. Which reactor is experiencing the most negative reactivity from equilibrium core Xe-135? A. Reactor A due to a greater concentration of equilibrium core Xe-135. B. Reactor A due to lower competition from the fuel for thermal neutrons. C. Reactor B due to a greater thermal neutron flux in the core. D. Reactor B due to a smaller accumulation of stable fission product poisons.
B.
A nuclear reactor has been operating at 50 percent power for one week when power is quickly ramped (over 4 hours) to 100 percent. How will the core xenon-135 concentration respond? A. Decrease initially, then build to a new equilibrium concentration in 8 to 10 hours B. Increase steadily to a new equilibrium concentration in 20 to 30 hours C. Decrease initially, then build to a new equilibrium concentration in 40 to 50 hours D. Increase steadily to a new equilibrium concentration in 70 to 80 hours
C.
A nuclear reactor has been operating at a steady-state power level for 15 hours following a rapid power reduction from 100 percent to 50 percent using boration for reactivity control. Which one of the following describes the current core Xe-135 concentration? A. Increasing B. Decreasing C. At equilibrium D. Oscillating
B.
A nuclear reactor was operating for 42 weeks at a stable reduced power level when a reactor trip occurred. The reactor was returned to critical after 12 hours and then ramped to 60 percent power in 6 hours. How much time at steady state 60 percent power will be required to reach equilibrium xenon? A. 20 to 30 hours B. 40 to 50 hours C. 70 to 80 hours D. Unable to determine without knowledge of previous power history
B.
A nuclear reactor has been operating at 100 percent power for one week when power is ramped in 4 hours to 25 percent power. The new equilibrium core xenon-135 level will be ____________ the initial 100 percent equilibrium value. A. the same as B. about 80 percent of C. about 50 percent of D. less than 25 percent of
C.
A nuclear reactor has been operating at a constant power level for 15 hours following a rapid power reduction from 100 percent to 50 percent. Which one of the following describes the current core xenon-135 concentration? A. Increasing toward a peak. B. Decreasing toward an upturn. C. Increasing toward equilibrium. D. Decreasing toward equilibrium.
D.
A nuclear reactor was operating for 24 weeks at a constant power level when a reactor trip occurred. The reactor was returned to critical after 12 hours and then ramped to 80 percent power in 6 hours. Approximately how much time at steady state 80 percent power will be required to reach equilibrium core xenon-135? A. 10 to 20 hours B. 40 to 50 hours C. 70 to 80 hours D. Cannot determine without knowledge of previous power history
B.
A nuclear reactor has been operating at 100 percent power for two weeks when power is decreased to 10 percent in one hour. Immediately following the power decrease, core xenon-135 concentration will ____________ for a period of ____________. A. decrease; 4 to 6 hours B. increase; 4 to 6 hours C. decrease; 8 to 11 hours D. increase; 8 to 11 hours
D.
A nuclear reactor is initially operating at 50 percent of rated power with equilibrium core xenon-135. Power is increased to 100 percent over a one hour period and average reactor coolant temperature is adjusted to 588EF using manual rod control. Rod control is left in manual and no subsequent operator actions are taken. Considering only the reactivity effects of core xenon-135 changes, which one of the following describes the average reactor coolant temperature 8 hours after the power change is completed? A. Greater than 588EF and decreasing slowly B. Greater than 588EF and increasing slowly C. Less than 588EF and decreasing slowly D. Less than 588EF and increasing slowly
A.
A nuclear reactor had been operating at 100 percent power for two weeks when power was reduced to 10 percent over a one hour period. In order to maintain plant parameters stable during the next 24 hours, which one of the following incremental control rod manipulations will be required? A. Withdraw rods slowly during the entire period. B. Withdraw rods slowly at first, then insert rods slowly. C. Insert rods slowly during the entire period. D. Insert rods slowly at first, then withdraw rods slowly.
B.
A nuclear reactor had been operating at 50 percent power for two weeks when power was increased to 100 percent over a 3-hour period. In order to maintain reactor power stable during the next 24 hours, which one of the following incremental control rod manipulations will be required? A. Withdraw rods slowly during the entire period. B. Withdraw rods slowly at first, then insert rods slowly. C. Insert rods slowly during the entire period. D. Insert rods slowly at first, then withdraw rods slowly.
D.
Which one of the following explains why core Xe-135 oscillations are a concern in a nuclear reactor? A. They can adversely affect core power distribution and they can require operation below full rated power. B. They can adversely affect core power distribution and they can prevent reactor criticality during a reactor startup. C. They can cause rapid reactor power changes during power operation and they can require operation below full rated power. D. They can cause rapid reactor power changes during power operation and they can prevent reactor criticality during a reactor startup.
A.
A nuclear reactor had been operating at 70 percent power for two weeks when power was increased to 100 percent over a 2-hour period. To offset Xe-135 reactivity changes during the next 12 hours, which one of the following incremental control rod manipulations will be required? A. Withdraw rods slowly during the entire period. B. Withdraw rods slowly at first, then insert rods slowly. C. Insert rods slowly during the entire period. D. Insert rods slowly at first, then withdraw rods slowly.
D.
A nuclear reactor is initially operating at 100 percent power with equilibrium core xenon-135. Power is decreased to 50 percent over a 1-hour period and average reactor coolant temperature is adjusted to 572EF using manual rod control. Rod control is left in Manual and no subsequent operator actions are taken. Considering only the reactivity effects of core xenon-135 changes, which one of the following describes the average reactor coolant temperature 10 hours after the power change is completed? A. Less than 572EF and increasing slowly. B. Less than 572EF and decreasing slowly. C. Greater than 572EF and increasing slowly. D. Greater than 572EF and decreasing slowly.
A.
A nuclear reactor is initially operating at 80 percent power with equilibrium core xenon-135. Power is increased to 100 percent over a 2-hour period and average reactor coolant temperature is adjusted to 585EF using manual rod control. Rod control is left in Manual and no subsequent operator actions are taken. Considering only the reactivity effects of core xenon-135 changes, which one of the following describes the average reactor coolant temperature 24 hours after the power change is completed? A. Less than 585EF and decreasing slowly. B. Less than 585EF and increasing slowly. C. Greater than 585EF and decreasing slowly. D. Greater than 585EF and increasing slowly.
A.
A nuclear reactor is initially operating at 100 percent power with equilibrium core xenon-135. Power is decreased to 40 percent over a 2 hour period and average reactor coolant temperature is adjusted to 562EF using manual rod control. Rod control is left in Manual and no subsequent operator actions are taken. If only the reactivity effects of core xenon-135 changes are considered, which one of the following describes the status of the average reactor coolant temperature 2 hours after the power change is completed? A. Greater than 562EF and decreasing slowly. B. Greater than 562EF and increasing slowly. C. Less than 562EF and decreasing slowly. D. Less than 562EF and increasing slowly.
C.
Two identical nuclear reactors have been operating at a constant power level for one week. Reactor A is at 50 percent power and reactor B is at 100 percent power. If both reactors trip/scram at the same time, Xe-135 will peak first in reactor ______ and the highest Xe-135 reactivity peak will occur in reactor ______. A. A; B B. A; A C. B; B D. B; A
A.
Two identical nuclear reactors have been operating at a constant power level for one week. Reactor A is at 100 percent power and reactor B is at 50 percent power. If both reactors trip/scram at the same time, Xe-135 will peak first in reactor ______ and the highest Xe-135 reactivity peak will occur in reactor ______. A. A; B B. A; A C. B; B D. B; A
D.
A nuclear reactor has been operating at 75 percent power for two months. A manual reactor trip is required for a test. The trip will be followed immediately by a reactor startup with criticality scheduled to occur 12 hours after the trip. The greatest assurance that fission product poison reactivity will permit criticality during the startup will exist if the reactor is operated at ____________ power for 48 hours prior to the trip and if criticality is rescheduled for ____________ hours after the trip. A. 100 percent; 8 B. 100 percent; 16 C. 50 percent; 8 D. 50 percent; 16
D.
Select the combination below that completes the following statement. The amount of control rod withdrawal needed to overcome peak core xenon-135 negative reactivity will be smallest after a reactor trip from equilibrium _______ reactor power at the _______ of core life. A. 20 percent; beginning B. 20 percent; end C. 100 percent; beginning D. 100 percent; end
A.
Select the combination below that completes the following statement. The amount of control rod withdrawal needed to compensate for peak core xenon-135 negative reactivity will be greatest after a reactor trip from equilibrium _______ reactor power at the _______ of core life. A. 20 percent; beginning B. 20 percent; end C. 100 percent; beginning D. 100 percent; end
D.
A nuclear reactor has been operating at 80 percent power for two months. A manual reactor trip is required for a test. The trip will be followed by a reactor startup with criticality scheduled to occur 24 hours after the trip. The greatest assurance that xenon reactivity will permit criticality during the reactor startup will exist if the reactor is operated at ____________ power for 48 hours prior to the trip and if criticality is rescheduled for ____________ hours after the trip. A. 60 percent; 18 B. 60 percent; 30 C. 100 percent; 18 D. 100 percent; 30
B.
A nuclear reactor trip occurred one hour ago following several months of operation at 100 percent power. Reactor coolant temperature is being maintained at 550EF and the source range count rate is currently 400 cps. Assume a constant shutdown neutron flux. If no operator action is taken, how will the source range count rate respond during the next 24 hours? A. The count rate will remain about the same. B. The count rate will decrease for the entire period. C. The count rate will initially decrease and then increase. D. The count rate will initially increase and then decrease.
C.
Slow changes in axial power distribution in a nuclear reactor that has operated at a steady-state power for a long time can be caused by xenon... A. peaking. B. override. C. burnup. D. oscillation.
D.
Xenon oscillations that tend to dampen themselves toward equilibrium over time are ______________ oscillations. A. converging B. diverging C. diffusing D. equalizing
A.
Which one of the following occurrences can cause reactor power to fluctuate between the top and bottom of the core when steam demand is constant? A. Steam generator level transients B. Iodine spiking C. Xenon oscillations D. Inadvertent boron dilution
C.
A nuclear reactor has been operating at 100 percent power for several weeks with a symmetrical axial power distribution that is peaked at the core midplane. Reactor power is reduced to 50 percent using boration to control reactor coolant temperature while maintaining control rods fully withdrawn. During the power reduction, the axial power distribution will... A. shift toward the top of the core. B. shift toward the bottom of the core. C. peak at the top and the bottom of the core. D. remain symmetrical and peaked at the core midplane.
A.
A nuclear reactor is operating at 100 percent power at the beginning of core life with equilibrium core xenon-135. Reactor power is reduced, within a 2 hour period, to 50 percent. Control rods are maintained fully withdrawn. The following parameter values are given: Prior to After Power Change Power Change Reactor power: Reactor coolant system boron concentration: Control rod position: 100 percent 740 ppm Fully Withdrawn 50 percent 820 ppm Fully Withdrawn What is the effect on power distribution in the core during the first 4 hours following the power reduction? A. Power production in the top of the core increases relative to the bottom of the core. B. Power production in the top of the core decreases relative to the bottom of the core. C. There is no relative change in power distribution in the core. D. It is impossible to determine without additional information.
A.
When a nuclear reactor experiences xenon oscillations, the most significant shifts in power generation occur between the ________________ of the core. A. top and bottom B. adjacent quadrants C. center and periphery D. opposite quadrants
A.
A nuclear reactor has been operating at 80 percent power for several weeks with power production equally distributed axially above and below the core midplane. Reactor power is increased to 100 percent using boron dilution to control reactor coolant temperature while maintaining control rods fully withdrawn. During the power increase, axial power distribution will... A. shift toward the top of the core. B. shift toward the bottom of the core. C. remain evenly distributed above and below the core midplane. D. peak at the top and the bottom of the core.
B.
Which one of the following will cause reactor power to fluctuate slowly between the top and bottom of the core with steady state steam demand? A. Feedwater variations B. Dropped center control rod C. Xenon oscillation D. Samarium oscillation
C.
Xenon-135 oscillations take about ____________ hours to get from maximum xenon-135 negative reactivity to minimum xenon-135 negative reactivity. A. 40 to 50 B. 24 to 28 C. 12 to 14 D. 6 to 7
C.
A nuclear reactor is operating at 80 percent power at the beginning of core life with equilibrium core xenon-135. Reactor power is increased, over a 2-hour period, to 100 percent. The following information is provided: Prior toPower Change After Power Change Reactor power: Reactor coolant system boron concentration: Control rod position: 80 percent 780 ppm Fully Withdrawn 100 percent 760 ppm Fully Withdrawn What is the effect on power distribution in the core during the first 4 hours following the power increase? A. Power production in the top of the core increases relative to the bottom of the core. B. Power production in the top of the core decreases relative to the bottom of the core. C. There is no relative change in power distribution in the core. D. It is impossible to determine without additional information.
B.
A nuclear reactor has been operating at full power for one month following a refueling outage with core axial neutron flux distribution peaked in the bottom half of the core. An inadvertent reactor trip occurs. The reactor is restarted, with criticality occurring 6 hours after the trip. Reactor power is increased to 60 percent over the next 4 hours and stabilized. How will core axial neutron flux distribution be affected during the 1-hour period immediately following the return to 60 percent power? The core axial neutron flux peak will be located __________ in the core than the pre-trip peak location, and the flux peak will be moving ___________. A. higher; downward B. higher; upward C. lower; downward D. lower; upward
A.
A nuclear power plant is being returned to operation following a refueling outage. Fuel preconditioning requires reactor power to be increased from 10 percent to full power gradually over a one week period. During this slow power increase, most of the positive reactivity added by the operator is required to overcome the negative reactivity from... A. fuel burnup. B. xenon buildup. C. fuel temperature increase. D. moderator temperature increase.
B.
A nuclear reactor has been shut down for seven days to perform maintenance. A reactor startup is performed and power level is increased to 50 percent over a 5-hour period. When power reaches 50 percent, the magnitude of core xenon negative reactivity will be... A. increasing toward a peak value. B. increasing toward an equilibrium value. C. decreasing toward an equilibrium value. D. decreasing toward an upturn.
B.
A nuclear reactor has been shut down for 5 days to perform maintenance. A reactor startup is performed and power is ramped to 75 percent over a 16 hour period. When power reaches 75 percent, the concentration of core xenon-135 will be... A. decreasing toward an upturn. B. increasing toward a peak value. C. decreasing toward an equilibrium value. D. increasing toward an equilibrium value.
D.
A nuclear reactor was shut down for seven days to perform maintenance. A reactor startup was performed, and power level was increased from 1 percent to 50 percent over a two hour period. Ten hours after reactor power reaches 50 percent, the magnitude of core xenon-135 negative reactivity will be... A. increasing toward a downturn. B. increasing toward an equilibrium value. C. decreasing toward an equilibrium value. D. decreasing toward an upturn.
B.
A nuclear reactor startup is being performed 5 hours after a reactor trip from 100 percent equilibrium power. The nuclear power plant is being returned to rated power at 2.0 percent/minute instead of the normal rate of 0.5 percent/minute. At the faster rate of power increase, the minimum amount of core xenon will occur ____________ and the amount of equilibrium core xenon will be ____________. A. sooner; the same B. sooner; smaller C. later; the same D. later; smaller
A.
A nuclear reactor has been operating at 100 percent power for eight weeks when a reactor trip occurs. The reactor is critical 6 hours later and power is increased to 100 percent over the next 6 hours. What is the status of core xenon-135 concentration when power reaches 100 percent? A. Increasing toward an equilibrium value. B. Burning out faster than it is being produced. C. Increasing toward a peak value. D. At equilibrium.
B.
Xenon poisoning in a nuclear reactor core is most likely to prevent a reactor startup following a reactor shutdown from ____________ power at the ____________ of core life. A. high; beginning B. low; beginning C. high; end D. low; end
C.
A nuclear power plant startup is in progress 5 hours after a reactor trip from 100 percent equilibrium power. The power plant is currently at 10 percent power and being returned to 100 percent power at 0.25 percent per minute instead of the normal rate of 0.5 percent per minute. At the slower rate of power increase, the maximum amount of core xenon-135 will occur ____________ than normal; and the amount of equilibrium core xenon-135 at 100 percent power will be ____________. A. sooner; the same B. sooner; smaller C. later; the same D. later; smaller
C.
A nuclear reactor that has been operating at rated power for two weeks is quickly reduced in power to 50 percent. Xenon-135 will reach a new equilibrium condition in ______________ hours. A. 8 to 10 B. 20 to 25 C. 30 to 35 D. 40 to 50
D.
A nuclear reactor that has been operating at rated power for about two weeks is reduced in power to 50 percent. What happens to the Xe-135 concentration in the core? A. There will be no change because iodine concentration is constant. B. Xenon will initially build up, then decrease to a new equilibrium value. C. Xenon will initially decrease, then build up to a new equilibrium value. D. Xenon will steadily decrease to a new equilibrium value.
B.
Which one of the following describes the change in core xenon-135 concentration immediately following a power increase from equilibrium conditions? A. Initially decreases due to the increased rate of xenon-135 radioactive decay. B. Initially decreases due to the increased absorption of thermal neutrons by xenon-135. C. Initially increases due to the increased xenon-135 production from fission. D. Initially increases due to the increased iodine-135 production from fission.
B.
A nuclear reactor has been operating at steady-state 50 percent power for 12 hours following a one- hour power reduction from steady-state 100 percent power. Which one of the following describes the current core xenon-135 concentration? A. Increasing toward a peak B. Decreasing toward an upturn C. Increasing toward equilibrium D. Decreasing toward equilibrium
D.
A nuclear reactor that had been operating at 100 percent power for about two months was shutdown over a 2-hour period. Following the shutdown, core xenon-135 will reach a long-term steady-state concentration in ______________ hours. A. 8 to 10 B. 20 to 25 C. 40 to 50 D. 70 to 80
D.
A nuclear reactor has been operating at steady-state 30 percent power for 3 hours following a one- hour power reduction from steady-state 100 percent power. Which one of the following describes the current core xenon-135 concentration? A. Increasing toward a peak B. Decreasing toward an upturn C. Increasing toward equilibrium D. Decreasing toward equilibrium
A.
A nuclear power plant is initially operating at equilibrium 100 percent power in the middle of a fuel cycle. The operators decrease main generator load while adding boric acid to the reactor coolant system (RCS) over a period of 30 minutes. At the end of this time period, reactor power is 70 percent and average reactor coolant temperature is 575EF. All control rods remain fully withdrawn and in manual control. Given: Total reactivity added by operator = -3.3 x 10-3 ¥K/K Total power coefficient = -1.1 x 10-4 ¥K/K/% power Assuming no additional RCS boration occurs and no other operator actions are taken, which one of the following describes the average reactor coolant temperature after an additional 60 minutes? A. 575EF and stable. B. Less than 575EF and increasing. C. Less than 575EF and decreasing. D. Less than 575EF and stable.
C.
A nuclear reactor has been operating at 70 percent power for 20 hours following a one-hour power reduction from steady-state 100 percent power. Which one of the following describes the current core xenon-135 concentration? A. Increasing toward a peak. B. Decreasing toward an upturn. C. Decreasing toward equilibrium. D. At equilibrium.
C.
Compare a nuclear reactor that has been operating at 50 percent power for several days when a reactor trip occurs, to a reactor that had been operating at full power prior to the trip. For the reactor at 50 percent power, xenon would peak _____________ and the peak xenon reactivity would be ______________. A. earlier; the same B. at the same time; the same C. earlier; less negative D. at the same time; less negative
C.
Following a reactor trip, negative reactivity from xenon initially increases due to... A. xenon production from the decay of iodine-135. B. xenon production from the spontaneous fission of uranium. C. the reduction of xenon removal by decay. D. the reduction of xenon removal by recombination.
A.
Twenty four hours after a reactor trip from a long-term, steady-state, 100 percent power run, the core xenon-135 concentration will be approximately... A. the same as at the time of the trip and decreasing. B. the same as at the time of the trip and increasing. C. 50 percent lower than at the time of the trip and decreasing. D. 50 percent higher than at the time of the trip and increasing.
A.
A nuclear reactor has been operating at full power for several days when it is shut down rapidly (within 2 hours) for maintenance. How will core xenon reactivity change? A. Peak in 2 to 4 hours and then decay to near zero in about 1 day. B. Peak in 2 to 4 hours and then decay to near zero in 3 to 4 days. C. Peak in 6 to 10 hours and then decay to near zero in about 1 day. D. Peak in 6 to 10 hours and then decay to near zero in 3 to 4 days.
D.
A nuclear reactor has been operating at 100 percent power for three weeks when a reactor trip occurs. Which one of the following describes the concentration of Xe-135 in the core 24 hours after the trip? A. At least 2 times the concentration at the time of the trip and decreasing B. Less than ¥ the concentration at the time of the trip and decreasing C. At or approaching a peak value D. Approximately the same as at the time of the trip
D.
Fourteen hours after a reactor trip from 100 percent power equilibrium xenon conditions, the amount of core xenon-135 will be... A. lower than 100 percent equilibrium xenon, and will have added a net positive reactivity since the trip. B. lower than 100 percent equilibrium xenon, and will have added a net negative reactivity since the trip. C. higher than 100 percent equilibrium xenon, and will have added a net positive reactivity since the trip. D. higher than 100 percent equilibrium xenon, and will have added a net negative reactivity since the trip.
D.
How does core xenon-135 change immediately following a reactor trip from equilibrium 100 percent power operation? A. Decreases due to xenon removal by decay. B. Decreases due to the reduction in xenon production directly from fission. C. Increases due to xenon production from the decay of iodine-135. D. Increases due to xenon production from the spontaneous fission of uranium.
C.
Given: ¥ A nuclear reactor was operating at 100 percent power for six weeks when a reactor trip occurred. ¥ A reactor startup was performed and criticality was reached 16 hours after the trip. ¥ Two hours later, the reactor is currently at 30 percent power with control rods in Manual. If no operator actions are taken over the next hour, average reactor coolant temperature will ___________ because core Xe-135 concentration is ___________. A. increase; decreasing B. increase; increasing C. decrease; decreasing D. decrease; increasing
A.
A nuclear reactor has been operating at 100 percent power for two months when a reactor trip occurs. Four hours later, the reactor is critical and stable at 10 percent power. Which one of the following operator actions is required to maintain reactor power at 10 percent over the next 18 hours? A. Add positive reactivity during the entire period B. Add negative reactivity during the entire period C. Add positive reactivity, then negative reactivity D. Add negative reactivity, then positive reactivity
C.
After a reactor shutdown from equilibrium core xenon conditions, the maximum xenon -135 negative reactivity (height of the xenon peak) is _______________ the pre-shutdown equilibrium power level. A. independent of B. directly proportional to C. inversely proportional to D. dependent on but not directly proportional to
D.
A nuclear power plant was shut down following three months of operation at full power. The shutdown occurred over a 3 hour period with a constant rate of power decrease. Which one of the following describes the reactivity added by core xenon during the shutdown? A. Xenon buildup added negative reactivity. B. Xenon buildup added positive reactivity. C. Xenon burnout added negative reactivity. D. Xenon burnout added positive reactivity.
A.
Four hours after a reactor trip from equilibrium full power operation, a reactor is taken critical and power is immediately stabilized for critical data. To maintain a constant reactor power, the operator must add __________ reactivity because core Xe-135 concentration is __________. A. positive; increasing B. positive; decreasing C. negative; increasing D. negative; decreasing
A.
A nuclear power plant has been operating at 100 percent power for two months when a reactor trip occurs. Shortly after the reactor trip a reactor startup is commenced. Six hours after the trip, reactor power is at 2 percent. To maintain power stable at 2 percent over the next hour, the operator must add... A. positive reactivity because core xenon-135 is building up. B. negative reactivity because core xenon-135 is building up. C. positive reactivity because core xenon-135 is decaying away. D. negative reactivity because core xenon-135 is decaying away.
A.
Following a seven day shutdown, a reactor startup is performed and the nuclear power plant is taken to 100 percent power over a 16-hour period. After reaching 100 percent power, what type of reactivity will the operator need to add to compensate for core xenon-135 changes over the next 24 hours? A. Negative only B. Negative, then positive C. Positive only D. Positive, then negative
C.
A nuclear reactor has been operating at 100 percent power for two weeks. Power is then decreased over a 1-hour period to 10 percent. Assuming manual rod control, which one of the following operator actions is required to maintain a constant reactor coolant temperature at 10 percent power during the next 24 hours? A. Add negative reactivity during the entire period B. Add positive reactivity during the entire period C. Add positive reactivity, then negative reactivity D. Add negative reactivity, then positive reactivity
C.
A nuclear reactor startup is being conducted and criticality has been achieved 15 hours after a reactor trip from long term operation at full power. After 1 additional hour, reactor power is stabilized at 10-4 percent power and all control rod motion is stopped. Which one of the following describes the response of reactor power over the next 2 hours without any further operator actions? A. Power increases toward the point of adding heat due to the decay of Xe-135. B. Power increases toward the point of adding heat due to the decay of Sm-149. C. Power decreases toward the shutdown neutron level due to the buildup of Xe-135. D. Power decreases toward the shutdown neutron level due to the buildup of Sm-149.
A.
A nuclear reactor is initially shut down with no xenon in the core. Over the next four hours, the reactor is made critical and power level is increased to the point of adding heat. The shift supervisor has directed that power be maintained constant at this level for 12 hours for testing. To accomplish this objective, control rods will have to be... A. inserted periodically for the duration of the 12 hours. B. withdrawn periodically for the duration of the 12 hours. C. inserted periodically for 4 to 6 hours, then withdrawn periodically. D. withdrawn periodically for 4 to 6 hours, then inserted periodically.
B.
A nuclear reactor is initially shut down with no xenon in the core. A reactor startup is performed and 4 hours later power level is at 25 percent. The shift supervisor has directed that reactor power and reactor coolant temperature be maintained constant at this level for 12 hours. To accomplish this, control rods will have to be... A. withdrawn periodically for the duration of the 12 hours. B. inserted periodically for the duration of the 12 hours. C. withdrawn periodically for 4 to 6 hours, then inserted periodically. D. inserted periodically for 4 to 6 hours, then withdrawn periodically.
A.
A nuclear reactor is operating at 100 percent power immediately following a one-hour power ascension from steady-state 70 percent power. To keep reactor coolant system temperature stable over the next two hours, the operator must ________ control rods or _________ reactor coolant boron concentration. A insert; increase B. insert; decrease C. withdraw; increase D. withdraw; decrease
A.
A nuclear reactor is operating at 60 percent power immediately after a one-hour power increase from equilibrium 40 percent power. To keep the average reactor coolant temperature stable over the next two hours, the operator must ________ control rods or _________ reactor coolant boron concentration. A. insert; increase B. insert; decrease C. withdraw; increase D. withdraw; decrease
A.
A nuclear power plant is initially operating at 100 percent power with equilibrium core xenon-135. Power is decreased to 75 percent over a 1-hour period and then stabilized. The operator then adjusts control rod height as necessary to maintain average reactor coolant temperature constant. What will be the rod position and directional trend 30 hours after the power change? A. Above the initial 75 percent power position and inserting slowly B. Above the initial 75 percent power position and withdrawing slowly C. Below the initial 75 percent power position and inserting slowly D. Below the initial 75 percent power position and withdrawing slowly
C.
A nuclear power plant had been operating at 100 percent power for two months when a reactor trip occurred. Soon afterward, a reactor startup was performed. Twelve hours after the trip, the startup has been paused with reactor power at 2 percent. To maintain reactor power and reactor coolant temperature stable over the next hour, the operator must add ___________ reactivity because core xenon-135 concentration will be _____________. A. positive; increasing. B. negative; increasing. C. positive; decreasing. D. negative; decreasing.
D.
A nuclear power plant is initially operating at steady-state 100 percent reactor power in the middle of a fuel cycle. The operators then slowly decrease main generator load to 90 percent while adding boric acid to the RCS. After the required amount of boric acid is added, reactor power is 90 percent and average reactor coolant temperature is 582EF. All control rods remain fully withdrawn and in manual control. Assuming no other operator actions are taken, which one of the following describes the average reactor coolant temperature after an additional 60 minutes? A. Higher than 582EF and increasing slowly. B. Higher than 582EF and decreasing slowly. C. Lower than 582EF and increasing slowly. D. Lower than 582EF and decreasing slowly.
D.